Touch Sensing

Touch is the point of physical contact between a user and an interactive system.

Type of sensors

There are many ways to sense touch using either analogue sensors or digital ones. The easiest way is obviously using a switch button, and if that is good enough for your application, then you are lucky! Otherwise please find following a summarised list of possibilities...

Force-sensitive sensors - They are variable resistors that convert mechanical force into electrical resistance. They are very easy to use and should be connected to an Analogue Input channel. In general they require a firm but slightly flexible support to work properly.

Flex sensors - They are variable resistors that convert bending into electrical resistance. In many ways they are very similar to Force-sensitice sensors.

Capacitance sensors - Ideal to sense the slightes touch, like in mobile phone touch screens. Our body acts as a capacitor, storing a small electric charge. These sensors can be tuned for touch sensing or near touch sensing.

Piezoelectric sensors - These are used to measure slight force changes and strain, they react very quickly and produce a change in voltage. Piezos are challenging to use as they sometimes operate in voltage ranges of thousands and yet produce small changes of microvolts.

Optical sensors - Most notably LDR (light dependent resistors) are variable resistors that change valu according to the amount of light that reaches them. Can be used for crude tracking or for a contactless button.